GB1592446A

GB1592446A - Series coupling for springs

Info

Publication number: GB1592446A
Application number: GB11655/78A
Authority: GB
Original assignee: Lockheed Electronics Co Inc
Current assignee: Lockheed Electronics Co Inc
Priority date: 1977-03-23
Filing date: 1978-03-23
Publication date: 1981-07-08
Also published as: BE865263A; IT1093489B; CA1072934A; IT7821505A0; US4145016A; FR2384701A1; DE2812932A1

Description

PATENT SPECIFICATION

( 11) 1 592 446 ( 21) Application No 11655/78 ( 22) Filed 23 March 1978 ( 31) Convention Application No.

780319 ( 32) Filed 23 March 1977 in ( 33) United States of America (US) ( 44) Complete Specification published 8 July 1981 ( 51) INT CL 3 B 65 H 23/20 G 11 B 15/43/115/2815/44 ( 52) Index at acceptance B 8 M 682684687 D G 5 R B 37 Y B 476 B 481 B 482 B 483 B 488 B 493 ND NJ NK ( 54) SERIES COUPLING FOR SPRINGS ( 71) We, LOCKHEED ELECTRONICS COMPANY INC a corporation organised under the laws of the State of California, United States of America, of U S Highway 22, Plainfield, New Jersey 07061, United

States of America, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the following statement:

This invention relates to the coupling together of two or more springs in series and more particularly to the coupling of such springs in connection with the take-up and supply reels of a web system.

In the prior art, negator springs have been used to supply the differential motion between supply and take-up reels of a capstan driven web system Since the number of turns such springs provide is limited, it has been necessary to couple such springs together in order to increase the number of spring turns available to provide sufficient tension for long tape lengths In the prior art, such springs have been coupled together by means of gearing, belts or chains However, these prior art techniques prove disadvantageous because the added complexity of gears, belts or chains results in decreased reliability and increased cost and weight of the web system Since such web systems are typically used in space applications, reliability, cost and weight are highly important factors.

An object of this invention is to provide a means for serially coupling springs without the use of gears, belts or chains.

Another object of this invention is to provide a means for creating web tension in a capstan driven reel system wherein negator springs are serially coupled together without the use of gears, belts or chains.

Another object of this invention is to provide improved means for creating web tension in a capstan driven reel system which is capable of smoothing surge changes in tape tension to avoid "looping" when subjected to rapid changes in tape speed.

It is another object of the invention to provide a simplified method for increasing the tape storing capacity of a capstan driven reel system.

According to the present invention, there is provided an apparatus for applying tension between two movable members, the 55 said apparatus comprising a coupling arm rotatably mounted between said members, at least one pair of spring storage drums rotatably carried on the coupling arm, and a torsional spring for each of the storage 60 drums connecting one of the storage drums to one of the two members and the other of the storage drums to the other of the two members.

A web system incorporating the preferred 65 embodiment of the invention is illustrated in the drawing The web apparatus includes a supply reel 11 and a take-up reel 13 Each reel 11, 13 has a hub 17, 18 and rotates freely on a central shaft 15 The reel hubs 70 17, 18 are disposed inwardly, facing each other A capstan 19 draws tape 20 off a supply reel 11 around a guide roller 21 In order to maintain tension on the tape 20 and drive the supply reel 11, a spring coupling 75 apparatus 23 embodying the preferred embodiment of the invention is located between the hubs 17, 18 of the supply and take-up reels 11, 13.

This coupling apparatus 23 employs a 80 coupling arm 25 rotatably carried intermediate its ends on central shaft 15 through bearing 28 This bearing 28 permits the coupling arm 25 to rotate freely with respect to the central shaft 15 One end of the cou 85 pling arm 25 mounts a pair of spring storage shafts 27, 29, while the other end of the coupling arm 25 mounts a second pair of spring storage shafts 31, 33.

Each of the four storage shafts 27, 29, 31, 90 33 carries a drum 50, 51, 52, 53 on which one end of a negator spring 35, 37, 39, 41 is attached thereto Drums 0, 51, 52 and 53 are free to rotate on its shaft Thus, negator springs 35, 37 are mounted about the hub 95 17 of supply reel 11, and negator springs 41, 39 are mounted about the hub 18 of the take-up reel 13 Negator springs 35, 41 make up one spring pair and negator springs 37, 39 make up the other spring pair in 100 e 1 i 1 592 446 spring coupling apparatus 23 representing the preferred embodiment The free ends of negator springs 35, 37 are attached to the hub of the supply reel 11 such that relative motion of the hub 17 with respect to the storage shafts 27, 31 in an unwind (supply) direction causes the springs 35, 37 to wind onto the hub 17 Negator springs 41, 39 are similarly attached to the hub 18 of the take-up reel 13 such that motion of the take-up reel 13 in a take-up direction relative to the spring storage shafts 29, 33 causes the springs 39, 41 to wind onto hub 18 As well known in the art, negator springs are springs designed to apply a constant spring force or tension as they wind or unwind.

As thus connected, the coupling apparatus 23 operates to provide the requisite differential motion of the tape reels as tape is wound from one reel to another and effectively doubles the available turns for winding the tape web on the reels The use of two pairs of springs 35, 41 and 37, 39 effectively doubles the torque applied to the reel hubs 17, 18 Initially the take-up reel 13 must rotate at a higher velocity than the supply reel 11 This differential motion is provided while maintaining essentially constant tape tension as springs 39, 41 unwind from the take-up reel hub 18 while springs 35, 37 unwind from the supply reel hub 17.

As the tape diameter on each reel nears equality, the unwinding of the springs 35, 37, 39, 41 slows At the centre of the tape, there is no winding of any of the springs 35, 37, 39, 41 Past the centre of the tape, the supply reel 11 begins to rotate faster than the take-up reel When this occurs, springs 35, 37, 39, 41 rewind onto reel hubs 17, 1-.

When the tape direction is reversed, the same process occurs in the reverse direction as the springs unwind from their respective storage drums 50, 51, 52, 53.

By mounting sp ring storage drums 50, 51, 52, 53 on arm 25 through shafts 27, 29, 31, 33 and allowing the arm to rotate freely about central shaft 15, springs 35, 41 and 37, 39 constitute two pairs of series coupled springs wherein the two springs in a pair share the differential motion of the reels to double the available spring turns for winding the web on the reels, thus increasing the tape storage capacity of the web system By using two pairs of springs rather than only one pair, web tension is doubled.

An additional benefit flowing from the series coupling of the negator springs through arm 25 is that the web system will, due to inertia effects, maintain a more constant tape tension in the presence of tape speed variations than will a conventional system where the spring or springs are directly coupled between reels.

In a modification, two or more springs 65 may be employed in combinations other than the two series pairs shown, and the spacing between the assembly of parts along central shaft 15, as well as the physical dimensions and relative proportions of the 70 parts themselves, may be changed to meet particular design requirements.

Claims

WHAT WE CLAIM IS:-

1 An apparatus for applying tension between two movable members, the said 75 apparatus comprising a coupling arm rotatably mounted between said members, at least one pair of spring storage drums rotatably carried on the coupling arm, and a torsional spring for each of the storage drums 80 connecting one of the storage drums to one of the two members and the other of the storage drums to the other of the two members.

2 An apparatus as claimed in Claim 1 85 wherein the two members and the coupling arm are mounted on a common support shaft for rotation about the shaft.

3 An apparatus as claimed in claim 2 comprising a drum shaft spaced from the 90 support shaft and connecting the storage drums to the coupling arm for orbital movement about the supporting shaft.

4 An apparatus as claimed in any of the preceding claims wherein each spring is a 95 negator spring.

An a paratus as claimed in any of the preceding c Saims wherein the two members are web transport reels.

6 A capstan driven web system having a 100 take-up reel and a supply reel coaxially mounted for rotation about a support shaft and an apparatus for providing tension on the web between the two coaxial reels, the said apparatus comprising a coupling arm 105 mounted for rotation about the support shaft between the two reels, an even number of spring storage shafts mounted on the coupling arm, and a plurality of torsional springs equal in number to the storage 110 shafts, each of the springs being mounted to a respective storage shaft by a first end, the second ends of half of the springs being connected to the supply reel and the second ends of the other half of the springs being 115 connected to the take-up reel.

7 An apparatus as claimed in claim 6 also comprising a drum mounted on each of the storage shafts, the springs having their first ends connected to their respective drum 120 for storage thereon.

8 A capstan driven web system having a 1 592 446 take-up reel and a supply reel coaxially mounted for rotation about a support shaft, and apparatus for providing tension on the web between the two reels substantially as herein described with reference to the accompanying drawings.

ELKINGTON AND FIFE, Chartered Patents Agents, High Holborn House, 52-54 High Holborn, London WC 1 V 65 H.

Agents for the Applicants.

Printed for Her Majesty's Stationery Office by The Tweeddale Press Ltd, Berwick-upon-Tweed, 1981 Published at the Patent Office, 25 Southampton Buildings, London, WC 2 A 1 l AY, from which copies may be obtained.